Structural beam for ceiling suspension system

ABSTRACT

A structural beam member comprising a pair of elongated metal strips disposed in side-by-side abutting relationship to form an upstanding web, an elongated rib joining the top of the strips, and an elongated flange extending laterally from each side of the base of the web, so that the beam has substantially an inverted tee cross section. The web portion includes an expansion relief space of generally rectangular configuration. The margins of the expansion relief space, parallel to the longitudinal axes of the flange and rib portions, have opposed cutout triangular notches extending into the web and rib portions. A strap of the web portion longitudinally spans the expansion relief space. The width of the web strap tapers inwardly from both ends so that the web strap is narrowest at its middle.

United States Patent [72] inventor Michael J. Kedel Baltimore, Md. 211Appl. No. 867,553 [22) Filed Oct. 20, 1969 [45} Patented June 29, 1971[73) Assignee Eastern Products Corporation Columbia. Md.

[54] STRUCTURAL BEAM FOR CEILING SUSPENSION SYSTEM 10 Claims, 5 DrawingFigs. [52] US. Cl 52/232, 52/495. 52/573,52/D1G. 5 [51] Int. Cl E04c2/42, E04b 1/98 [50] Field ofSearch 52/232, 573, DIG. 5. 495

[56] References Cited UNITED STATES PATENTS 3,175,655 3/1965 Brown etal52/232 3,189,139 6/1965 Znamirowski et al. 52/232 3.388.519 6/1968Downing 52/573 3,496.690 2/l970 .lahn 52/573 Primary ExaminerF rank L.Abbott Assistant Examiner-James L. Ridgill, Jr. AtlorneyCharles B. SmithABSTRACT: A structural beam member comprising a pair of elongated metalstrips disposed in side-by-side abutting relationship to form anupstanding web, an elongated rib joining the top of the strips, and anelongated flange extending laterally from each side of the base of theweb, so that the beam has substantially an inverted tee cross section.The web portion includes an expansion relief space of generallyrectangular configuration. The margins of the expansion relief space,parallel to the longitudinal axes of the flange and rib portions, haveopposed cutout triangular notches extending into the web and ribportions. A strap of the web portion longitudinally spans the expansionrelief space. The width of the web strap tapers inwardly from both endsso that the web strap is narrowest at its middle.

PATENTEU JUNZS 1971 F'IGI.

F'IGJ.

STRUCTURAL BEAM FOR CEILING SUSPENSION SYSTEM BACKGROUND OF THEINVENTION The present invention relates to a structural beam membercharacterized by means for isolating thermal expansion deformation to aparticular portion of the beam. More particularly the present inventionrelates to structural beams used in suspended ceiling constructions inwhich a metallic grid system is suspended from primary ceiling membersand used to support acoustical tiles or other ceiling panels.

In recent years it has been common in the construction of new buildingsand in the renovation of old buildings to employ suspended ceilings inwhich acoustical tiles or other types of panels are supported by flangedbeams, usually made of steel or aluminum. In most such systems theflanged beams are arranged in a rectangular grid system with longparallel beams, called main runners," being joined at suitable intervalsby transverse parallel beams called cross T's. In some systems thebottom flange of the metal beams forms a part of the visible ceilingsurface while in others the metal beams are not visible after theceiling panels are installed.

When the metal beams of a ceiling suspension system are subjected tohigh temperatures which accompany fires, the metallic beams undergo aconsiderable increase in length. Unless means are provided for absorbingthe increase in length due to thermal expansion, long structural memberstend to bend and twist, dropping the ceiling panels on to the floorbeneath. Thus, even though these ceiling panels may be highly resistantto fire conditions, much of the fire-retarding advantage of such panelsis lost when some or all of the panels fall due to twisting of thesuspension system. In many cases, twisting of the beam in a directiontransverse of its length but in the plane of the ceiling may actuallybreak the ceiling panels.

The present invention provides a structural beam member characterized inthat under exposure to extremely high tem peratures, longitudinalexpansion is controlled and isolated to a particular point in the beamwhere the expansion is accommodated without twisting of the beam. Thisis accomplished by cutting away portions of the beam at the point whereit is desired to localize the expansion of the beam. l'he shape of thiscutout portion is designed so as to minimize the weakening of the beamat this point and yet provide for controlled distortion of the beamduring thermal expansion. Additional features of the construction of thepresent invention are a relatively simple design and economicalmanufacture and installation.

A preferred embodiment of the present invention comprises a pair ofelongated metal strips disposed in side by side abutting relationship toform an upstanding web, an elongated rib joining the top of the strips,and an elongated flange ex tending laterally from each side of the baseof the web, so that the beam has substantially an inverted tee crosssection. The web portion includes an expansion relief space of generallyrectangular configuration. The margins of the expansion relief space,parallel to the longitudinal axes of the flame and rib portions, haveopposed cutout triangular notches extending into the web and ribportions. the notches along the expansion space margin nearest theflange portion do not extend to the plane of the upper surface of theflange portion; thus there is a narrow portion of the web structure atall points between the edge of the expansion relief space and uppersurface of the flange. This narrow portion of the web adds to thesupportive strength of the beam without significantly interferring withthe controlled deformation of the beam on thermal expansion.

A strap of the web portion longitudinally bridges the expansion reliefspace. The width of the web strap tapers inwardly from both ends so thatthe web strap is narrowest at its middle. This tapered design insuresthat the web strap will buckle at its midpoint and deform in a planeparallel to the plane of the flange on thermal expansion.

SUMMARY OF THE INVENTION A structural beam member comprising a pair ofelongated metal strips disposed in side by side abutting relationship toform an upstanding web, an elongated rib joining the top of the strips,and an elongated flange extending laterally from each side of the baseof the web, so that the beam has substantially an inverted tee crosssection.

The web portion includes an expansion relief space of generallyrectangular configuration. The margin of the expansion relief space,parallel to the longitudinal axes of the flange and rib portions, haveopposed cutout triangular notches extending into the web and ribportions. The notches along the expansion space margin nearest theflange portion extend to a point above the plane of the upper surface ofthe flange portion; there is some portion of the web structure at allpoints between the edge of the expansion relief space and the flange.

A strap of the web portion longitudinally spans the expansion reliefspace. The width of the web strap tapers inwardly from both ends so thatthe web strap is narrowest at its middle to insure that the web strapwill buckle at its midpoint on thermal expansion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational viewillustrating one form of beam construction in accordance with theinvention;

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1;

FIG. 3 is a bottom plan view of a length of sheet metal illustrating apreblanking operation in the formation of the beam of FIG. 1;

FIG. 4 is a perspective view of the beam of FIG. 1;

FIG. 5 is a perspective view of the beam of FIG. 1 after deformation dueto thermal expansion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,and more particularly to FIGS. 1, 2 and 4, there is illustrated atypical suspended ceiling beam 10 embodying the invention. It could beused as either a main runner or cross tee, although usually it will be amain runner. The beam 10 is normally formed from relatively thincold-rolled steel and is comprised of an upstanding web 12 formed fromvertical portions 14 and 15 joined at the top by a rounded or bulbousrib 16. In other embodiments the rib 16 is of rectangular configuration.The web portions 14 and 15 are provided with outwardly extending, panelsupporting flanges l8 and 19, respectively. As best shown in FIG. 2, thebeam in cross section has essentially an inverted tee shape. Adecorative flange cover 20 caps the flanges l8 and 19 to provide anattractive under surface for installations where it is a visible part ofthe installed ceilings.

Only a short length of the beam 10 is shown in the drawings. In the caseof a main runner, the beam 10 might typically be 8 or 12 feet long,while in the case ofa cross tee, beam 10 might typically be 2 or 4 feetlong.

The web 12 of the beam 10 is provided with a longitudinally extendingcutout portion which may be termed an expansion relief space or rout 22.The expansion relief rout 22 is of a generally rectangular shape. InFIG. 1 the lines 22a, 22b, 22c, and 22d form an illustrative rectangularborder for the expan' sion relief rout 22. The line 22a runs parallelto, and is located nearly adjacent to the top margin of the verticalportion 14 of the web 12. The line 220 is parallel to, and is located adistance A from the line 22a and a distance B from the bottom of theflange 18. Lines 22b and 22d are perpendicular to, and intersect lines2211 and 22b, respectively, and are a distance C apart. The axialdimension C is dependent upon the coeffcient of expansion of the beammetal, upon the length of the beam, upon the number of relief sectionsto be provided in the beam and upon the maximum temperature to beaccommodated. For purposes of illustration the lines 22a-22d are notshown in FIG. 1 as coinciding with the margins of the expansion reliefrout 22, however, the dimensions A B and C are based on the actualmargins of the expansion relief space 22 of the embodiment of thedrawings. For a 12 foot length of beam l inches high, the distance Amight typically be 0.970 inches, the distance B might typically be 0.265inches, and the distance C might typically be 2,000 inches. The typical12- foot beam of the embodiment shown in the drawings has one suchexpansion relief rout 22 spaced near a beam end. The vertical center ofthe expansion relief rout 22 (shown as line 22 in FIG. 1) is located 6inches from one end of the beam 10.

Within the expansion relief rout 22, a portion 24 of the web 12 near therib 16 is cut out. A portion 26 of the web 12 near the flanges 18 and 19is also cut out, leaving a web strap 28 which horizontally spans theexpansion relief rout 22 between the cutout portions 24 and 26. The webstrap 28 is narrowest at its center 30 and has an outward taper towardboth ends 32 and 33 which are bounded by the lines 2211 and 22b,respectively. This tapered design insures that the web strap will buckleat its midpoint on thermal expansion. The web strap ends 32 and 33 havefillets 34 and 35, respectively,joining the web strap 28 to the web 12.The web strap 28 is comprised of two side by side portions 36 and 37which are formed from the vertical portions 14 and 15, respectively.

A vee-shaped notch 38 extends from the reference line 22c into the web12, with its vertex directed toward, but not reaching, the flanges l8and 19. The notch 38 is located directly opposite the web strap centerpoint 30. The angular opening of the notch 38 might typically be 120.

A pair of right-triangular notches 40 and 41 also extend from thereference line 22c into the web 12 toward, but not touching, the flanges18 and 19. The right angle of the notch 40 is located approximately atthe intersection of the lines 220 and 22d. One margin of the notch 40 isparallel to the line 22d and the other margin forming the hypotenusemight typically be at 30 to the line 220. The right angle of the notch41 is located approximately at the intersection of the lines 22b and22c. One margin of the notch 41 is parallel to the line 22b and theother margin forming the hypotenuse might typically be at 30 to the line22c. A small portion 39 of the web 12 remains between the notches 38 and40. Likewise, a small portion 43 of the web 12 remains between thenotches 38 and 41. These web portions 39 and 43 add to the supportivestrength of the beam 10.

A vee-shaped notch 42 is cut out of the web 12 and the rib 16 directlyopposite the notch 38. The notch 42 extends from the line 220 throughapproximately five-eighths of the rib 16. The angular opening of thenotch 42 might typically be I20". A pair of right-triangular notches 44and 45 also extend from the reference line 22a into the web 12 and therib 16. The right angle of the notch 44 is located approximately at theintersection of the lines 22a and 22d. One margin of the notch 44 isparallel to the line 22d and the other margin forming the hypotenusemight typically be at 30 to the line 22a. The right angle of the notch45 is located approximately at the intersec tion of the lines 220 and22b. One margin of the notch 45 is parallel to the line 22b and theother margin forming the hypotenuse might typically be at 30 to the line22a.

The notches 44 and 45 extend approximately halfway through the rib 16. Asmall portion 46 of the web 12 and a portion 58 of the rib 16 remainbetween the notches 42 and 44. Likewise, a small portion 47 of the web12 and a portion 59 of the rib 16 remain between the notches 42 and 45.The web portions 46 and 47 add to the structural integrity of the beamin normal use.

The web 12 is provided with generally rectangular routes 48 spacedperiodically along the beam 10 which engage cross tee members. The web12 is also provided with holes 50 to accommodate the wires usually usedfor suspending the beam 10 from the ceilingjoists or other primarysupports.

Referring now to FIG. 3, the beam 10 is shown in developed form, i.e.,as a flat sheet of metal 52, and hence HO. 3 represents the beam stockbefore rolling. The lines 54 and 55 represent the locations of the linesof intersection between the flange 18 and the vertical web portion 14and between the flange 19 and the vertical web portion 15, respectively.The lines 56 and 57 represent the upper margins of the vertical webportions 14 and 15, respectively.

The cutout portions 24A and 24B are aligned when the beam 10 is rolledto form the cutout space 24. The cutout portions 26A and 26B are alignedwhen the beam 10 is rolled to form the cutout space 26. Likewise, thecutout portions 48A, 48B, and 50A, 50B are aligned when the beam 10 isrolled to form the rectangular routes 48 and the holes 50, respectively.In other embodiments the beam 10 is first rolled from a plain sheet ofmetal to have a tee cross section and then the various holes, notchesand expansion relief spaces are stamped out. In still other embodimentsof the present invention the beam 10 is extruded as a solid piece in atee cross section. The various routs, holes, notches, and expansionrelief spaces discussed above are then cut out of the beam.

Referring now to FIG. 5 the beam 10' is illustrated after exposure tofire conditions. High temperatures expand the beam 10 longitudinally,and because its ends are restrained by the building walls or by abuttingbeams, the beam 10' acts as though a compressive, longitudinal force hadbeen applied.

This results in a shortening of the length of the expansion relief space22'. Because the web strap 28 is tapered toward the middle, the verticalportions 36 and 37, of which it is comprised, buckle outward away fromthe plane of the web 12. Although the vertical portions 36' and 37' areshown as buckled in opposite directions the controlled expansion will beachieved equally as well if they buckle together in the same direction.The strap will normally be above the tops of the supported ceilingtiles.

The expansion forces in the flanges 18' and 19' and in the verticalportions 14' and 15 will produce bending in the weakest portions inpreference to stiffer portions. The notch 38' is the weakest part in thelower portion of the beam 10 and hence the expansion forces tend toclose the vee-shaped notch 38. This is illustrated in FIG. 5 where thevee-shaped notch 38' has a decreased angular opening. This decrease inthe angular opening is produced by the downward deformation of the webportions 39 and 43 and the adjacent flange portions. The deformationalso results in an expansion of the angular openings of the notches 40'and 41 Likewise, the weakest spot of the upper portion of the beam 10'is the notch 42'. Upon longitudinal thermal expansion the angularopening of the notch 42 decreases. This results from the upwarddeformation of the rib portions 58 and 59 and the associated webportions 46' and 47'. The deformation also increases the angularopenings of the notches 44 and 45', The resulting beam distortion thustakes place at a predetermined point in the beam and in the horizontaland vertical planes, without radical twisting of the beam, so that theceiling panels do not break or drop from lack of support.

While the invention has been described in connection with specificembodiments thereof and in specific uses, various modifications thereofwill occur to those skilled in the art without departing from the spiritand scope of the invention as set forth in the appended claims.

What 1 claim is:

l. A beam for use in a fire-retarding structural system, comprising arib portion, a horizontal flange portion, and an upstanding web portionwhich joins the rib portion to the flange portion, the web portionhaving an opening forming an expansion relief space, the space beingpositioned intermediate the ends of the beam, the expansion relief spacehaving a length taken along the length of the beam selected toaccommodate anticipated axial expansion of the web portion upon exposureto a fire to thereby prevent twisting of such web portion and theexpansion relief space including an upper and a lower margin, the webportion having triangular notches extending from the lower margin to apoint above the flange portion, the web and the rib portion havingtriangular notches extending from the upper margin of the expansionrelief space, the expansion relief space having a web strap whichbridges the expansion relief space, the web strap having an inward tapersuch that it is narrowest at its middle, whereby the flange portionbuckles downwardly, the rib portion buckles upwardly, and the web strapbuckles outwardly when the beam is exposed to fire.

2. A beam for use in a fire-retarding structural system comprising a ribportion, an elongated flange portion, and an up standing web portionjoining the flange and rib portions, the web portion including anopening forming a generally rectangular expansion relief space, theexpansion relief space having a first margin parallel to thelongitudinal axis of the flange portion and located near the flangeportion and a second margin parallel to the longitudinal axis of the ribportion and located near the rib portion, the first and second marginshaving opposed cutout triangular notches extending into the web and ribportions, the web having a strap portion longitudinally spanning therelief space, the width of the strap tapering inwardly from both endssuch that said strap is narrowest at its middle.

3. A beam as set forth in claim 2 including fillets for joining thestrap portion to the web portion.

4. A beam as set forth in claim 2 in which a pair of the opposed notchesare vee shaped and longitudinally centered along the first and secondmargins of the expansion relief space.

5. A beam as set forth in claim 4 in which the notches extending fromthe first margin extend toward the flange portion to a point above theflange portion.

6. A structural beam member comprising a pair of elongated metal stripsdisposed in side by side abutting relationship to form an upstandingweb, an elongated rib joining the top of the strips, and an elongatedflange extending laterally from each side of the base of the web, theweb portion including an opening of a generally rectangularconfiguration forming an expansion relief space, the expansion reliefspace having a first margin parallel to the longitudinal axis of the ribportion and a second margin parallel to the longitudinal axis of theflange portion, the first and second margins having cutout triangularnotches extending into the rib and web portions, a strap of the webportion longitudinally spanning the expansion relief space, the width ofthe strap tapering inwardly from both ends such that the strap isnarrowest at its middle, whereby the flange portion buckles downwardly,the rib portion buckles upwardly, and the strap buckles outwardly whenthe beam is exposed to fire.

7. A beam as set forth in claim 6 in which a pair of the notches are veeshaped and located opposite each other at the longitudinal center of theexpansion relief space.

8. A beam as set forth in claim 6 in which the expansion relief spacehas four corners, the margins of the expansion relief space at eachcorner forming an acute angle.

9. A beam as set forth in claim 6 in which a portion of the web existsat all points between the notches extending from the lower margin of theexpansion relief space and the flange portion.

10. A beam as set forth in claim 6 including fillets forjoining the endsof the strap to the web portion.

1. A beam for use in a fire-retarding structural system, comprising arib portion, a horizontal flange portion, and an upstanding web portionwhich joins the rib portion to the flange portion, the web portionhaving an opening forming an expansion relief space, the space beingpositioned intermediate the ends of the beam, the expansion relief spacehaving a length taken along the length of the beam selected toaccommodate anticipated axial expansion of the web portion upon exposureto a fire to thereby prevent twisting of such web portion and theexpansion relief space including an upper and a lower margin, the webportion having triangular notches extending from the lower margin to apoint above the flange portion, the web and the rib portion havingtriangular notches extending from the upper margin of the expansionrelief space, the expansion relief space having a web strap whichbridges the expansion relief space, the web strap having an inward tapersuch that it is narrowest at its middle, whereby the flange portionbuckles downwardly, the rib portion buckles upwardly, and the web strapbuckles outwardly when the beam is exposed to fire.
 2. A beam for use ina fire-retarding structural system comprising a rib portion, anelongated flange portion, and an upstanding web portion joining theflange and rib portions, the web portion including an opening forming agenerally rectangular expansion relief space, the expansion relief spacehaving a first margin parallel to the longitudinal axis of the flangeportion and located near the flange portion and a second margin parallelto the longitudinal axis of the rib portion and located near the ribportion, the first and second margins having opposed cutout triangularnotches extending into the web and rib portions, the web having a strapportion longitudinally spanning the relief space, the width of the straptapering inwardly from both ends such that said strap is narrowest atits middle.
 3. A beam as set forth in claim 2 including fillets forjoining the strap portion to the web portion.
 4. A beam as set forth inclaim 2 in which a pair of the opposed notches are vee shaped andlongitudinally centered along the first and second margins of theexpansion relief space.
 5. A beam as set forth in claim 4 in which thenotches extending from the first margin extend toward the flange portionto a point above the flange portion.
 6. A structural beam Membercomprising a pair of elongated metal strips disposed in side by sideabutting relationship to form an upstanding web, an elongated ribjoining the top of the strips, and an elongated flange extendinglaterally from each side of the base of the web, the web portionincluding an opening of a generally rectangular configuration forming anexpansion relief space, the expansion relief space having a first marginparallel to the longitudinal axis of the rib portion and a second marginparallel to the longitudinal axis of the flange portion, the first andsecond margins having cutout triangular notches extending into the riband web portions, a strap of the web portion longitudinally spanning theexpansion relief space, the width of the strap tapering inwardly fromboth ends such that the strap is narrowest at its middle, whereby theflange portion buckles downwardly, the rib portion buckles upwardly, andthe strap buckles outwardly when the beam is exposed to fire.
 7. A beamas set forth in claim 6 in which a pair of the notches are vee shapedand located opposite each other at the longitudinal center of theexpansion relief space.
 8. A beam as set forth in claim 6 in which theexpansion relief space has four corners, the margins of the expansionrelief space at each corner forming an acute angle.
 9. A beam as setforth in claim 6 in which a portion of the web exists at all pointsbetween the notches extending from the lower margin of the expansionrelief space and the flange portion.
 10. A beam as set forth in claim 6including fillets for joining the ends of the strap to the web portion.